Fusarium dry rot of potato

The causative agent of potato dry rot is the fungus Fusarium caeruleum (along with other Fusarium species). It is a major fungal pathogen that primarily causes significant post-harvest losses. While it can cause wilting in the field, its most severe impact is seen in storage facilities where it spreads rapidly among harvested tubers.

This pathogen mainly affects potatoes, though it is capable of surviving on other solanaceous crops and common weeds. It is a soil-borne fungus that can persist for several years in the field, making it difficult to eradicate once it has established itself in the soil. The fungus survives as mycelium or chlamydospores, waiting for favorable conditions to infect a new host.

Symptoms begin as small, slightly depressed, dark or brown spots on the skin of the tuber. As the disease progresses, the underlying tissue dries out, becomes shrunken, and develops a powdery, corky texture. Hollow cavities often form within the affected tissue, which become lined with white, blue, or pinkish fungal mycelium and spore masses. Eventually, the tuber may become completely shriveled and mummified.

Environmental factors play a crucial role in disease development. High humidity, poor ventilation in storage, and relatively warm temperatures promote the growth of the fungus. The most critical entry point for the pathogen is any physical damage, such as bruising, cuts, or skin abrasions caused during harvesting and transportation, which allow the fungus to bypass the natural protective barriers of the potato skin.

Effective management requires an integrated approach to sanitation and crop handling:

• Minimizing mechanical damage during harvest and grading processes.
• Ensuring proper wound healing (curing) period before long-term storage.
• Strict monitoring of storage temperature and humidity to prevent condensation.
• Using certified, pathogen-free seed tubers.
• Implementing long-term crop rotation cycles to reduce soil-borne inoculum.